In a lead-acid battery for an idling-stop vehicle, the life of the battery may be ended due to breakage of a lug portion of a negative electrode plate. (Non-Patent Document 1: GS Yuasa Technical Report 6(1)7-13 (2009)).
A configuration of a negative electrode plate of a lead-acid battery will be described. An expanded grid, a punching grid, a casting grid and the like are known as current collectors. The expanded grid has frame ribs on the upper and lower parts of the grid, but has no frame ribs on the left and right parts. On the other hand, the cast grid and the punching grid each have frame ribs on the four peripheral sides of the grid. In addition, an organic expander such as lignin sulfonic acid or bisphenol condensation product is added to a negative electrode material. The organic expander prevents shrinkage of the negative electrode material, temporarily captures Pb2+ ions during charge and discharge, and improves low-temperature high rate discharge performance.